Object scaling preventing retargeting of rigify rig to bvh with MakeWalk
Apply Scale

The warning indicates the rig scale in object mode is not (1, 1, 1) (unity). Select the rig in object mode and press ctrl-A-S, or select via the Object &gt; Apply &gt; Scale  menu, to apply scale.

It's the same process as selecting all bones in edit mode and scaling to match the current size, with unity object scaling.